Doesn't work for me on "Two Node (Controller+Compute) Neutron GRE+OVS+Gluster Cluster" on F20 boxes with Havana manually installed via native repos. Have to run ifconfig eth0 mtu 1400 up via /etc/rc.d/rc.local to set the MTU to 1400.

Thanks a lot. It was just a typo in dhcp_agent.ini in line :-
dnsmasq_config_file = /etc/neutron/dnsmasq.conf
This typo clearly shows up in previous comment : dmasq_config_file = /etc/neutron/dnsmasq.conf <- wrong
Last line from dnsmasq.log :-
Mar 16 13:35:08 dnsmasq-dhcp[26111]: 1830014980 sent size: 2 option: 26 mtu 1454
Thank you once again.